222
O
R
EtO 2 C
EtO 2 C
R
H 3 CO 2 C
O
+
O
RO 2 C
O
1154 R = H
1155 R = CH 3
1156 R=H
1157 R=CH 3
1158 R = isobutyl
1159 R = n-butyl
1160 R = benzyl
1161 R = CH 2 CF 3
EtO 2 C
O
134
1141
1162
O
O
Scheme 21 Synthesis scheme for norketones by Muthukumarasamy et al.
The diketone 1164 was converted to 1168 via allylic alcohols 1166 and 1167.
Treatment of 1168 with allylic borane 1169 using palladium chemistry afforded
1171. Osmium oxidation furnished the 13-noreremophilanes 102 and 101. A norterpenoid 1170 was also synthesized starting from 1168.
The asymmetric synthesis of norsesquiterpenoids has been achieved by Abe
et al., using Shi’s method for the 1,4-diene 1173 derived from 2,6-dimethylbenzoic
acid (1172) (Scheme 23) [336]. The chiral epoxide 1174 thus prepared was converted to 1175. A Claisen rearrangement for the introduction of a two-carbon unit to
Scheme 22 Synthesis for norsesquiterpenoids 1164, 1165, 1170, 101, and 102 by Meng and Liu
M. Tori and C. Kuroda